Chemical and biological testing is commonly used to test for the presence or absence of chemical or biological agents. Testing for the presence of chemical or biological agents in blood, food or other materials is often performed to ensure safety or to facilitate diagnosis of medical conditions. For example, testing is used to identify chemicals, bacteria or other agents in blood samples taken from medical patients, laboratory samples developed for experimental purposes, food samples, or the like. In addition, chemical and biological testing is used to test for medical conditions such as pregnancy, diabetes, bacterial infection, and a wide variety of other conditions that may affect the patient's chemistry or biology.
One type of sensor that has been developed for chemical or biological sensing capabilities is a surface acoustic wave (SAW) sensor. One example of a SAW sensor is a Love mode shear-horizontal surface acoustic wave (SH-SAW) sensor. A SH-SAW sensor includes four main components: 1) a piezoelectric substrate; 2) an input inter-digitated transducer (IDT) on the substrate, which is used to excite an acoustic wave based on the piezoelectric effect; 3) an output IDT on the substrate, which receives the transmitted acoustic wave and generates electrical output by exploiting the piezoelectric effect; and 4) a wave-guide layer over the IDT's, which converts SH-type waves into waveguide Love modes for transmission from the input IDT to the output IDT. The presence of one or more materials on the surface of the SH-SAW sensor affects wave propagation through the waveguide layer in response to the presence of bacteria or other agents on the surface of the sensor, which facilitates detection of bacteria or other agents.